This invention is directed to a method for forming ceramics. More specifically, this invention is directed to a method for forming ceramics from paper residuals which are produced in the recycling of waste paper.
It has become common practice to recycle paper. This has advantages in both cost and environmental impact. The paper recycle process typically yields two dominant fractionsxe2x80x94paper fiber and paper residue. The paper fibers are reintroduced into the paper manufacturing process or utilized in the formation of refractory materials as described, for example, in U.S. Pat. No. 4,012,262. The paper residue fraction typically includes residual paper fibers and ceramic substances such as, for example, kaolin clay and ground calcium carbonate. Heretofore, the paper residue has been found to be of little commercial value.
The amount of paper fiber which is entrained in the paper residue fraction can generally be as high as 50-70%, by weight. Because of its limited commercial value, a large percentage of residue material is sent to landfills which is undesirable. Land-filling of the residuals is not only undesirable for the environment but the cost associated with disposal is a considerable expense to generators of the residual. The full financial and environmental impact of paper recycling cannot be realized until some commercial use of the paper residual is developed.
The manufacture of insulating firebrick is well known in the art. There are two predominant methods employed depending on the density and porosity of firebrick desired.
In one method of forming firebrick, mixtures are made of kaolin clay, sawdust and a gypsum (CaSO42H2O) binder. The mixture hardens to a low density mass which is formed and fired. The firing causes combustion of the saw dust leaving a porous ceramic. A particular problem associated with this material is the incorporation of gypsum which liberates sulfur dioxide and sulfur trioxide when fired. The sulfur compounds, collectively known as SOx, are highly undesirable and must be removed from the emission stack by scrubbing or the amount of material manufactured must be limited to remain under legal limits of SOx emissions. There has been a long felt desire in the art to modify, or eliminate, this process in favor of one which has lower SOx emissions.
In another method of forming firebrick a previously fired lightweight refractory aggregate is mixed with natural clays. The mixture is made into an appropriate shape by conventional methods, such as extrusion or pressing, and the shaped mixture is fired. This produces a higher density product which has inferior insulating properties to the aforementioned process. One advantage is the lower level of undesirable emissions.
Previously, the artisan has been forced to rely on methods which either generate undesirable emissions or materials with inferior insulating capabilities.
There has been a long felt need in the art to provide a method for manufacturing insulating firebrick which has adequate insulating capabilities and yet does not emit undesirable elements into the environment. The present invention provides such a process.
In another field of technology, solid-gas separations are usually conducted by a number of techniques involving the use inertial devices, such as cyclone separators, and filtration devices. In air pollution control equipment, a common technique is to use fabric filters in devices called collectively xe2x80x9cbag houses,xe2x80x9d which are well known in the art.
One problem with bag houses is that most conventional filtration materials cannot be used for gases exhibiting temperatures above 500xc2x0 F. For example, cotton cloth filters can be used up to 180xc2x0 F., Teflon(copyright) can be used to 450xc2x0 F., and fiberglass filters are appropriate for use up to 500xc2x0 F.
In some cases, it is practically impossible to reduce the temperature of input gases below 500xc2x0 F., or cold air must be injected in order to reduce the temperature of process exhaust. The latter practice necessitates large additional expense as a control device must be employed which has sufficient capacity to clean the larger total volume of input gas. Thus, there is a great need in the area of filtration technology for filtration materials and devices which are capable of withstanding temperatures above 500xc2x0 F.
Advantageously, the present invention provides a method for forming a ceramic which utilizes paper residuals.
It is also an advantage of the present invention that a method for forming a ceramic which has substantially low levels of sulfur compounds released during the manufacturing process is provided.
A particular feature of the present invention is that the properties of the material are substantially identical to previous materials which utilize gypsum and sawdust to form a calcium alumino-silicate ceramic.
It is a further advantage of the present invention that it provides a method for making a variety of insulating materials including insulating firebrick.
It is yet another advantage of the present invention that it provides a method for making novel filtration devices which are capable of high temperature solid-gas filtration.
These and other advantages, as will be realized, are provided in a method for making a low density ceramic. The method comprises the steps of:
a) providing a paper residual comprising from about 0.5 to about 99 percent, by weight, of at least one filler, from about 0 to about 20 percent, by weight, of a dye, from about 0 to about 10 percent, by weight, of an ink, from about 0.5 to about 99.5 percent, by weight, of paper fiber, and from about 0 to about 30 percent, by weight, of other components, based on a dry weight of the residual;
b) admixing a ceramic material with the paper residual, the ceramic material comprising up to about 90%, by weight, of the admixture, based on a dry weight of the admixture;
c) forming the admixture into a desired shape; and
d) firing the admixture to a temperature ranging from about 1850xc2x0 F. to about 2900xc2x0 F.
Another embodiment is provided in a method for making a lightweight aggregate comprising the steps of:
a) providing a paper residual comprising from about 10 to about 99 percent, by weight, of kaolin clay, from 0 to about 50 percent, by weight, calcium carbonate, and from about 0.5 to about 70 percent, by weight, paper fiber, based on a dry weight of the paper residual;
b) forming the paper residual into a temporary shape; and
c) firing the shaped paper residual to a temperature ranging from about 1850xc2x0 F. to about 2900xc2x0 F.
Yet another embodiment is provided in a method for making a ceramic material comprising the steps of:
a) providing a paper residual comprising from about 0.5 to about 99 percent, by weight, of at least one filler, from about 0 to about 20 percent, by weight, of a dye, from about 0 to about 10 percent, by weight, of an ink, from about 0.5 to about 99.5 percent, by weight, of paper fiber, and from about 0 to about 30 percent, by weight, of other components, based on a dry weight of the residual;
b) forming the paper residual into a temporary shape;
c) firing the shaped paper residual to a temperature ranging from about 1850xc2x0 F. to about 2900xc2x0 F. and pulverizing the fired mass to form a lightweight aggregate;
d) admixing a ceramic substance with the lightweight aggregate, the ceramic substance comprising up to about 90 percent, by weight, of the admixture, based on a dry weight of the admixture;
e) forming the admixture into a desired shape; and
f) firing the admixture to a temperature range from about 1850xc2x0 F. to about 2900xc2x0 F.; whereby sulfur-containing compounds are not substantially released during either of step c or f.
A particularly preferred product prepared by the present invention is a firebrick comprising calcium alumina-silicate prepared by a process comprising the steps of:
a) providing a paper residual comprising from about 0.5 to about 99 percent, by weight, of at least one filler, from about 0 to about 20 percent, by weight, of a dye, from about 0 to about 10 percent, by weight, of an ink, from about 0.5 to about 99.5 percent, by weight, of paper fiber, and from about 0 to about 30 percent, by weight, of other components, based on a dry weight of the residual;
b) admixing a ceramic substance with the paper residual, the ceramic substance comprising up to about 90%, by weight, of the admixture, based on a dry weight of the admixture;
c) forming the admixture into a desired shape; and
d) firing the admixture to a temperature ranging from about 1850xc2x0 F. to about 2900xc2x0 F.